Pointer input devices, such as mice, touch pads and the like have been integral parts of computer systems since the advent of graphical user interfaces. In many instances, such as self serve ticket vending terminals and automated teller machines, these devices are impractical and direct tactile contact with the computer screen is the preferred input mode. The variable display on the screen, coupled with the ability to sense the presence and position of a finger on the screen itself provides an efficient means for information entry, whether it is by display of a full keyboard for alpha-numeric entry such as ticket holder name or more limited “buttons” to press for selections, that can then be changed when a new screen is displayed. Use of such on-screen input, commonly termed “touch screen” technology eliminates moving parts and wearable contacts required for keyboards and physical buttons and switches and is ideal for many environments.
The touch screen as a tool for graphical user interface (GUI) with a computer is inherently more intuitive, and faster than alternatives such as the mouse or the light pen. The mouse or the light pen is precise but slow, translating the dexterity of the human hand to tedious positioning of a single indicator icon on a screen. The mouse or light pen is difficult to place briefly for high-speed applications such as music composition, game playing, and free hand drawing.
Touch screen technology has largely been implemented with transparent sheets placed over a display screen, wherein the sheets have variable electrical properties (capacitive, resistive, piezo-electric, acoustic, breakbeam IR) that can sense when pressure is applied to a particular area of the sheet. A drawback of the sensing sheets technologies is that the sheets are necessarily less hard and less durable than the glass or other clear panel of the underlying display. Hence these sheets are prone to wear and damage. The breakbeam IR gives false positives. Thus, there is a need for a reliable touch screen technology that works with a clear, sealed panel that is at least as durable as a typical display screen made of glass or acrylic.
Additional disadvantages of current touch screen technology are the high cost of large screens, degradation in screen clarity and excessive bulk that limits the ergonomic adjustment for access to large touch screens. The touch screens in current use are scalable to large size only with substantial increase in cost and bulk, and constrained in the number of simultaneous input positions that can be entered simultaneously, typically one.
Multiple-signal processing with rapid positioning would enable new applications such as rapid manual sorting and positioning of icons on the screen, game playing applications, document creation, music creation, art-work creation, multiple user use, and many other current and future applications.
The optical effect known as Frustrated Total Internal Reflection (FTIR) can be used to detect where an external object has touched a clear optical waveguide. Normally, light transmitted into the edge of a waveguide, which can be a simple flat piece of glass, will not escape the waveguide (e.g., the top or bottom surface of the transparent plastic or glass). When an object, such as a finger, is placed on the surface, however, the index of refraction (versus what was previously just air) is changed and the FTIR takes place. In such a case wherein light will now not be reflected at this point, and partly escapes from the wave guide. The light reflected from the finger is reflected in different directions, including through or out of the waveguide, and within the waveguide in different directions. For a flat piece of transparent plastic or glass, this effect would cause light to leave the surface of the transparent plastic or glass opposite of where a finger is placed. For example, if the edge of a sheet of transparent plastic or glass is evenly illuminated and one touched one surface of the transparent plastic or glass, the area under the point of contact would light up as viewed from under the point of contact. This optical phenomenon is well known, but to date, efficient, robust devices have not been developed to exploit FTIR to produce an effective touch screen input device. The wave guide can be flexible. So long as the material's flex stays within Snell's angle.